JPH09258044A - Optical filter-containing waveguide type optical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical filter-contg. waveguide type optical device which is low in excess loss at the time of packaging filter, has high reliability and high mass productivity. SOLUTION: The thin film-like multilayered filters are formed by direct vapor deposition on the end face 32a of a fiber array 32 or the end face of a waveguide substrate 30 or a multilayered filter chip which is a commercially marketed and finished product in place of the thin film-like multilayered filters is connected to the end face described above, by which the need for forming grooves for insertion of the filters to the waveguide substrate 30 or the extra spacings for the grooves is eliminated and, therefore, the number of stages is decreased and the excess loss is lessened. The fiber arrays 32, 39 and the end face of the waveguide substrate 30 are connected by adhesives to each other, thereby, the free expansion and contraction of the adhesives are made possible and, therefore, the occurrence of the trouble by peeling and air bubbles is obviated and the reliability is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a waveguide type optical device, and more particularly to a waveguide type optical device with a built-in optical filter.

[0002]

2. Description of the Related Art With the development of optical communication technology, various optical devices such as optical branching devices and optical demultiplexers have been developed. One of them is a waveguide type optical device with a built-in optical filter. This is a device in which an optical filter that transmits or reflects only signal light of a specific wavelength is built in a waveguide substrate having an optical waveguide formed in a plane.

FIG. 5 is a view showing a conventional example of a waveguide type optical device with a built-in optical filter (see, for example, JP-A-63-3371).
FIG. 6 is a view showing another conventional example of a waveguide type optical device with a built-in optical filter.

In the waveguide type optical device with a built-in optical filter shown in FIG. 5, 1 is a substrate, 2 is an optical waveguide formed on the substrate 1, 3 is a groove formed so as to intersect the optical waveguide 2, and 4 is a groove. An optical filter (interference film filter) inserted in the groove 3 is a directional coupler formed on the substrate 1, and 6 is an optical fiber connected to each optical waveguide 2 of the substrate 1.

In the waveguide type optical device with a built-in optical filter shown in FIG. 6, 10 is a plane substrate, and p ₁ , q ₁ , p ₂ , and q.
₂ , p ₃ , q ₃ , p ₄ , q ₄ are optical waveguides formed on the planar substrate 10, 11 is an optical waveguide p ₁ on the planar substrate 10,
Slits formed to cross q ₁ , p ₂ , q ₂ , p ₃ , q ₃ , p ₄ , q ₄ and A ₁ , A ₂ , A ₃ , A ₄ are optical branching couplers, B ₁ , B Reference numeral ₂ is a mark, and an optical filter (not shown) is inserted into the slit 11.

The optical devices shown in FIGS. 5 and 6 are
A slit is formed across the waveguide formed on the waveguide substrate, an optical filter is inserted into the slit, the position is adjusted, and then fixed with an adhesive or the like (waveguide substrate slit type). .

FIG. 7 is a view showing still another conventional example of a waveguide type optical device having an optical filter (for example, Japanese Patent Laid-Open No. 6-
59148 gazette).

The waveguide type optical device with a built-in optical filter shown in FIG. 1 has input waveguides 1a, 1a ', 2a,
2a ', 3a', 3a, 4a, 4a 'and output waveguide 1
b, 1b ', 2b, 2b', 3b, 3b ', 4b, 4b
'To form these waveguides 1a, 1a', 2a, 2a
′, 3a ′, 3a, 4a, 4a ′, 1b, 1b ′, 2
A plurality of optical fibers to be connected to b, 2b ', 3b, 3b', 4b, 4b 'are arranged on a V-groove substrate in which V-grooves are formed according to the core pitch of the substrate 20, and an optical fiber arranging tool (array) 21 and 22 are formed, a slit 23 is formed in the optical fiber array 21 on which the thin film filter is to be mounted, and a common filter is inserted into the slit 23 and fixed with an adhesive or the like. Incidentally, C ₁ , C ₂ , C ₃ , and C ₄ are waveguide type directional couplers (fiber array slit type).

[0009]

However, the conventional examples shown in FIGS. 5 and 6 have the following problems.

(1) When the slit is processed by a dicer with a rotary blade, chips around the slit, cracks, etc. occur,
When it reaches the waveguide core, the waveguide loss may increase or reflected return light may be generated.

(2) Since the slit width is larger than the filter thickness, diffraction loss occurs when passing through the slit. Further, since slits are collectively formed in the filter-unnecessary ports, diffraction loss occurs at the same time.

(3) It is necessary to adjust the position after placing the filter in the slit.

(4) When the adhesive for fixing the filter has high elasticity, cracks may occur at the ends of the slit lines of the waveguide substrate.

(5) If the adhesive for fixing the filter has low elasticity, peeling or bubbles may occur inside the adhesive.

Further, the conventional example shown in FIG. 7 has the following problems.

(6) Since a part of the fiber is cut and divided in a short fiber array having a length of several mm to several tens of mm, fixing of the fiber becomes insufficient, resulting in mechanical reliability, temperature cycle and high temperature. Environmental reliability such as high humidity decreases.

(7) Since the number of constituent parts is large and the structure is complicated, the manufacturing cost is high.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the above problems and to provide a waveguide type optical device with a built-in optical filter, which has a small excess loss at the time of mounting a filter, is highly reliable, and is highly producible. .

[0019]

In order to achieve the above object, the present invention has a built-in optical filter in which an optical filter is built in and a plurality of optical fibers are connected to a waveguide substrate on which a planar optical waveguide is formed. In a waveguide type optical device, an optical filter is formed on a connecting surface between a waveguide substrate and an optical fiber.

In addition to the above construction, the present invention provides an optical filter,
It may be formed by vapor deposition of a filter material on the end face of the waveguide substrate or the end face of the optical fiber.

In addition to the above structure, in the present invention, a multilayer filter chip may be used as an optical filter, and may be adhesively fixed between the end face of the waveguide substrate and the end face of the optical fiber.

That is, according to the present invention, the thin-film multilayer filter is formed by vapor deposition directly on the end face of the fiber array or the end face of the waveguide substrate, or a commercially available finished filter is connected.

(1) Reason for reducing excessive loss In the case of the prior art, it is preferable that the slit width formed in the waveguide substrate or the fiber array is narrower, but in consideration of workability at the time of inserting the filter, the filter thickness is several A surplus gap of approximately 20 μm was required. According to the present invention, since this excess gap is unnecessary, the excess loss of the device can be reduced to about 0.1 to 0.5 dB.

Further, a normal multilayer filter has a thickness of several μm.
Since it is formed on a substrate of m (for example, polyimide), the loss of the substrate (about 0.1 dB in the case of light-transmissive polyimide) is added when it is mounted as a chip. Therefore, when depositing a multilayer film directly on the end face of the waveguide substrate, 0.1 is required.
A reduction in excess loss of about dB is expected.

(2) Reason why reliability is improved In the prior art, either SiO ₂ or S having a small linear expansion coefficient is used.
A slit-shaped groove is formed in a waveguide made of i or the like, and an adhesive is filled in the groove. Since the linear expansion coefficient of the adhesive is much larger than that of the substrate material, the expansion of the high-elasticity type adhesive at the time of high temperature may cause a force to widen the slit groove to break the substrate. On the other hand, in the low elasticity type adhesive, shrinkage stress is generated inside the adhesive at low temperature, and peeling or bubbles may occur.

However, in the present invention, even when the fiber array and the end face of the waveguide substrate are connected by an adhesive,
Since the adhesive can freely expand and contract, the reliability due to the above-mentioned failure due to peeling and bubbles does not occur. However, it is desirable to use an adhesive having a linear expansion coefficient close to that of the multilayer filter.

(3) Reason why the number of steps is reduced The slit forming step, which was indispensable in the prior art, becomes unnecessary.
This is because when a multilayer film is formed by vapor deposition, hundreds of processes can be performed at one time.

[0028]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a diffusion exploded view showing an embodiment of a waveguide type optical device with an optical filter according to the present invention.
(A), (b) is process drawing of the optical filter used for the waveguide type optical device with a built-in optical filter shown in FIG.

In FIG. 1, reference numeral 30 denotes a four-circuit integrated type optical branching waveguide substrate as a waveguide substrate in which an optical waveguide 31 is formed on a planar substrate. This is a quartz substrate on which four-circuit couplers are formed by the flame deposition method, and the core pitch Pc at the input / output end face is about 250 μm.

Reference numeral 32 denotes an incident side fiber array, which is a V-groove block 34 in which eight parallel V-grooves 33 are formed on the surface of a quartz plate at a pitch of 250 μm similar to the core pitch Pc.
The optical fiber 36 from which the coating of the tape fiber 35 has been stripped is placed, the pressing plate 37 is loaded and integrated with the UV adhesive 38, and then the end face 32a is polished (FIG. 2).
(A)). In addition, the end surface 32a of the fiber array 32 is polished with an inclination of about 8 ° with respect to the vertical direction to prevent reflection. Further, as the tape fiber 35, two four-core tape fibers having different core coloring are used, the tip end portion of 20 to 40 mm is separated into a single core, and the fiber core wires are alternately arranged from a vertically stacked state of 4 cores × 2 stages, It is fan-shaped and formed into one row of eight cores.

Numeral 39 is an exit side fiber array, which is similar to the entrance side fiber array 32 in a V groove block 40 in which eight parallel V grooves are formed on the surface of a quartz plate at a pitch of 250 μm similar to the core pitch Pc. The optical fiber from which the coating of the tape fiber 41 has been stripped is placed, the pressing plate 42 is loaded and integrated with a UV adhesive, and then the end face is polished.

Although the end face of the output side fiber array 39 remains polished, the end face 3 of the input side fiber array 32 is kept.
A thin-film multilayer filter 43 is formed on a part of the optical fiber 36 on the 2a side. The thin-film multilayer filter 43 is masked except for the odd-numbered optical fibers 36, and T as a filter material is formed by an electron beam evaporation method.
About 30 layers of iO ₂ / SiO ₂ thin films are alternately laminated (thickness: about 10 μm), and for example, it blocks light having a wavelength of 1.5 μm band (FIG. 2B).

Both ends (No. 1, No. 8) of the two fiber arrays 32, 39 and the four-circuit integrated type optical coupling / branching waveguide substrate 30 are mounted on a precision alignment stage (not shown) capable of rotating three axes orthogonal to each other. The optical axis of only the optical fiber 36 is adjusted, and the end faces are connected with a UV adhesive to form a waveguide type optical device with a built-in optical filter. In addition, the four-circuit integrated optical coupling / branching waveguide substrate 30 and the fiber array 32,
The connecting method / means with the 39 is not limited to the UV adhesive, but other adhesives or guide connection with a fitting pin is also possible.

With this structure, it is not necessary to form a groove for inserting the filter into the waveguide substrate or an excess gap of the groove, so that the number of steps is reduced and excessive loss is reduced. In addition, the fiber arrays 32 and 39 and the waveguide substrate 3
By connecting the end surface of 0 with an adhesive,
Since the adhesive can freely expand and contract, no reliability due to peeling or bubbles does not occur and reliability is improved.

FIG. 3 is a diffusion exploded view showing another embodiment of the waveguide type optical device with a built-in optical filter of the present invention, and FIGS. 4A and 4B are the conductive filter built-in type shown in FIG. It is a process drawing of an optical filter used for a waveguide type optical device.
The same reference numerals are used for the same members as those in the embodiment shown in FIGS. 1 and 2.

The difference from the embodiment shown in FIGS. 1 and 2A and 2B is that the thin-film multilayer filter is not directly formed on the end face of the optical fiber by the electron beam evaporation method. The point is that a commercially available multilayer filter chip is used.

Of the fiber arrays 32 and 39 shown in FIG. 3, the end face of the output side fiber array 39 remains polished, and the multi-layer filter chip 44 is adhered to the end face of the incident side fiber array 32. .

The multilayer filter chip 44 is formed by laminating a Ti / SiO ₂ thin film on a light transmissive special polyimide film having a thickness of, for example, about 10 μm. Slit 44a that matches the fiber pitch by cutting in advance
It is formed in a comb-like shape having a groove (FIG. 4A). The multilayer filter chip 44 is bonded to the end surface of the incident side fiber array 32 after polishing with an optical system UV adhesive so that the odd-numbered optical fibers 36 are covered (FIG. 4B).

The subsequent deviceization process is similar to that of the embodiment shown in FIG.

In the above, the waveguide type optical device with a built-in optical filter has 1) the excessive loss due to the mounting of the filter is 0.1 to 10 times as compared with the conventional one.
It can be reduced by 0.5 dB. When only the multilayer film is directly formed on the waveguide substrate by vapor deposition, it is possible to further reduce 0.1 dB. This is because there is no excess gap before and after the filter.

2) When the filter is adhered and fixed, since the adhesive can freely expand and contract, there is no increase in loss due to cracking of the waveguide substrate or peeling of the adhesive. Further, since there is no slit groove processing by a dicer or the like, there is no increase in loss due to chipping of the core.

3) Since the slit groove processing is unnecessary, the processing man-hour is reduced.

4) When the filter is directly formed on the end surface of the fiber array or the waveguide substrate by vapor deposition, the filter can be manufactured and mounted at the same time. In addition, since batch processing is possible, it is possible to significantly reduce costs.

[0045]

In summary, according to the present invention, the following excellent effects are exhibited.

In a waveguide type optical device with a built-in optical filter in which an optical filter is built in and a plurality of optical fibers are connected to a waveguide substrate in which an optical waveguide is formed in a plane, the optical filter is composed of a waveguide substrate and an optical fiber. Since it is a thin-film multilayer filter formed on the connection surface with, it is possible to realize a waveguide type optical device with a built-in optical filter, which has a small excess loss when mounting the filter, is highly reliable, and is highly producible. .

[Brief description of drawings]

FIG. 1 is a diffusion exploded view showing an embodiment of a waveguide type optical device with a built-in optical filter of the present invention.

2A and 2B are process diagrams of an optical filter used in the waveguide type optical device with a built-in optical filter shown in FIG.

FIG. 3 is a diffusion exploded view showing another embodiment of the waveguide type optical device with a built-in optical filter of the present invention.

4A and 4B are process diagrams of an optical filter used in the waveguide type optical device with a built-in optical filter shown in FIG.

FIG. 5 is a diagram showing a conventional example of a waveguide type optical device with a built-in optical filter.

FIG. 6 is a diagram showing another conventional example of a waveguide type optical device with a built-in optical filter.

FIG. 7 is a diagram showing still another conventional example of a waveguide type optical device with a built-in optical filter.

[Explanation of symbols]

30 Waveguide substrate (4 circuit integrated type optical coupling / branching waveguide substrate,
Substrate) 32 Incident-side fiber array (fiber array) 39 Egress-side fiber array (fiber array) 43 Thin-film multilayer filter 44 Multi-layer filter chip

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Noriaki Takeya 3550 Kidayomachi, Tsuchiura City, Ibaraki Prefecture Hitachi Cable Ltd. System Materials Research Center

Claims (3)

[Claims] 1. A waveguide type optical device with a built-in optical filter, wherein an optical filter is built in and a plurality of optical fibers are connected to a waveguide substrate on which a planar optical waveguide is formed.
A waveguide-type optical device with a built-in optical filter, wherein the optical filter is formed on a connection surface between the waveguide substrate and the optical fiber. 2. A waveguide type optical device with a built-in optical filter according to claim 1, wherein the optical filter is formed on the end face of the waveguide substrate or the end face of the optical fiber by vapor deposition of a filter material. 3. A waveguide type optical device with a built-in optical filter according to claim 1, wherein a multilayer film filter chip is used as the optical filter, and is fixed by bonding between the end face of the waveguide substrate and the end face of the optical fiber.